Acoustics in granular porous media and the consolidation continuum.

One key influence on acoustic wave propagation in granular porous media is the degree to which the solid constituent grains can be treated as fully consolidated, weakly and/or partially consolidated, or entirely unconsolidated. Well‐known results of Gassmann and Biot all implicitly assume that the medium is fully consolidated, with welded contacts at the grain‐to‐grain interfaces. Such implicit assumptions are also present in standard bounding methods for elastic behavior, such as the Hashin‐Shtrikman bounds of elasticity. Influence of reductions in the degree of consolidation can be quantified for partially or weakly consolidated media, and granular media having no welded contacts can also be treated as porous media for sound waves in the Biot‐Gassmann sense when grains are experiencing sufficient overall confining stress. Methods recently developed to quantify wave propagation characteristics over the full range of possible behaviors in grain packs, as well as comparisons to experiments, will be presented.